Possibility of a simultaneously ferroelectric and magnetic phase transition

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1)From the results of magnetoelectric measurements, we concluded that the magnetic class of the low temperature phase of nickel-iodine boracite Ni^3B^7O^<13>I is m' or lower, in contrast with the previous view that it was m' m 2'. We suggested the existence of another phase transition of this crystal at 25 K. (to be published in Ferroelectrics)2)From the dielectric, magnetic and magnetoelectric measurements, weconcluded that EuMn_2O_5 show two phase transitions at 40 K and 21 K, respectively. The transition at 40K was considered to be of simultaneously ferroelectric and antiferromagnetic nature. Similar transition was also found in isomorphous BiMn_2O_5. The magnetic class of EuMn_23_5 below the second transition was determined to be m 1'. We discussed possible magnetic structures compatible with this symmetry. (to be published in Phase Transitions)3)From dielectric, magnetic and magnetoelectric measurements, weconcluded that GdMn_2O_5 shows two phase transitions at 39 K and 26 K, resp … More ectively. The transitionat 39Kwas considered to be of polar/non-polar type. Approximate magnetic class of this crystal below the second transition was determined to be m 2m 1'. The magnetoelectric effect of GdMn_2O_5 is one of the largest that have been reported previously. (submitted to Solid State Communications)4)We improved the detectionmethod of small ac magnetic moment that we developed previously. It may have a wide use in high temperature superconductivity study as well as in magnetoelectric measurement. (to be published in Phase Transitions)The results 2)and 3)show that rare earth manganites with the composition REMn_2O_5 are very interesting group of substances that possibly become ferroelectric and antiferro- or generally heli-magnetic simultaneously at a certain transition. We are now continuing a systematic study of this series of oxides.Along with the above research activities, the head investigator wrote a part of a review article about magnetoelectric effect with Drs. K. Siratori and E. Kita. (to be published in Acta Physica Polonica) Less